Mary Tyler Moore is standing by her longtime friend actress Valerie Harper as she faces terminal brain cancer. She is speaking out on her support for Harper whom she considers “a great girlfriend.”

"I'm absolutely devastated by this news," Moore tells People, adding: "Valerie has given so much joy, laughter and love to the world. I join her fans and send much love and positive thoughts to her and her family during this difficult time."

Harper, who was diagnosed with the cancer Jan. 15, previously battled lung cancer in 2009 and is now suffering from leptomeningeal carcinomatosis, where cancer cells spread into the membrane surrounding the brain.

One day before she announced her diagnosis, Harper told People that she called Moore to tell her that her cancer was incurable.

“Mary said, 'One day at a time,'" says Harper. "That's how we've got to live our lives. That's the best we can do."

Moore and Harper’s friendship has lasted since they co-starred together on the 1970s sitcom Mary Tyler Moore, where Valerie played Rhoda Morgenstern. Harper then went on to star in her own spinoff, Rhoda. Their relationship has grown to be more than just on camera for more than 30 years, and Moore says she admires Harper for her kind and generous personality.

This is not the first hurdle for their friendship as the actresses have overcome personal obstacles together in the past. Moore has had her share of challenges as well as she endured surgery in 2011 for a benign tumor in the same area where Harper’s cancer is located and has dealt with the deaths of both her sister and son.